Potential transformer



July 26, 1932. G. E. .JANssoN lPOTENTIAL TRANSFORMER Filed Deo. l, 1930Patented July 26, 1932 UNITED STATES PATENr orrie- GUSTAV E. JANSSON, OFATLANTIC, MASSACHUSETTS, ASSIGrNOR` TO CONDIT ELECTRICAL MANUFACTURINGCORPORATION, OF SOUTH BOSTON, MASSACHUSETTS, A CORPORA- TION OFMSSACHUSETTS POTENTIAL TRANSPORT/IER Application led December 1, 1930.Serial No, 499,142.

This invention relates to high tension power distribution systems, andparticularly to means for taking power at a low potential from a hightension circuit of the system.

The usual inductive potential transformer, when employed for very highvoltages, becomes very costly since it must be insulated to withstandthe full potential of the line, and it constitutes an object of thisinvention to provide a very simple and inexpensive potential transformerof the capacitive type suitable for deriving low tension power from veryhigh potential lines which also provides a greater security againstbreakdown of insulation than is possible with the usual high tensioninductive transformer without excessive provisions for insulation of theprimary winding thereof.

Capacitive transformers have been used where it was desired to obtainvery small amounts of low tension power to operate electrostatic voltmeters, synchroscopes and the like; but heretofore, it has not beenconsidered possible to obtain any sizeable current from a capacitivetransformer without the use of very large condensers which areprohibitive because of space limitations and expense.

It is a further object of the invention to provide a potentialtransformer ofthe capacitive type in combination with an inductivestepdown potential transformer of moderate voltages as unitary apparatuswhich is inexpensive and economical ofspace and which is capable ofproviding adequate low voltage power to perform all the operationsordinarily required of the presentinductive potential transformers, andwhich is also capableV of Vsupplying suicient power to permit phaseanglecorrection of the secondary voltage according to any of the well-knownmethods in use.

A further object of the invention is the provision of a potentialtransformer as above outlinedwhich does not present anydifficultproblems of insulation and which does not require the use ofexpensive high potential insulating; bushings.

A still further object is generally to improve the methods and apparatusfor deriving low tension power from high potential electrical` systems.

Fig. 1 is a sectional elevation of a capacitive potential transformerembodying the present invention.

Fig. 2 is a cross section taken along line 2-2 of Fig. 1.

Fig. 3 is a diagrammatic showing of the potential transforming elementsof the transformer.

As here shown, the potential transformer embodying the inventioncomprises an outer upstanding tubular casing including a lower metalbase portion 10, an intermediate metal portion 12, and an upperinsulating portion 14 having annular insulating capes 16 formed integraltherewith. Said lower base portion 10which is cylindrical inconfiguration, is provided at its bottom edge with an annular collar 18which has an outstanding flange 20 that provides a supporting base forthe casing. Said base. portion 10 is further provided with an integraloutstanding flange 22 at the top which provides an annular horizontalbase for the support of said intermediate casing portion 12 which isalso cylindrical but somewhat smaller in diameter than the base portion10 and which has an integral outstanding flange 24 at its bottom edgethat overlies the flange 22 of said base por-tion, whereby to supportthe intermediate portion 412 concentric with the base portion 10.Clamping bolts 26 extend through said flanges 22 and 24 to secure saidcasing portions together, a gasket 28 being provided between saidlianges to provide a fluid tight joint thereat. Said intermediate casingportion 12 is pro-vided with an annular collar 30 on the outer surfacethereof below its top edge. Said collar, which may be welded toV thecasing, has an outstanding flange 32 which is provided with anupstanding inte-4 gral annular flange 34 that is lconterminous with theupper end of the casing12 whereby to provide an annular open top recessat the upper end thereof in which the lower end of thevuper cylindricalinsulating portion 14 is received. A packing 36 is provided be tween theannular flange 32 and the bottom edge of the insulating shell 14 againstwhich mit packing said insulating portion 14 is permanently held in afluid tight manner by a body of cement 38 which permanently connects theintermediate and upper casing portions l2 and 14. An external metalcollar 40 is secured by a body of cement 42 to the upper end of saidinsulating portion 14 and has an inwardly directed annular flange 44which overlies the upper end of said insulating portion 14. Said collaralso has an outstanding annular flange 46 at its upper end to which adome-shaped metal cap y48 is detachably secured by means of peripheralclamping screws 50. The cap 48 has an annular horizontal rim 49 whichoverlies the attaching flange 46X and is provided with an annulardownturned lip 52`which extends below the attaching flange 46 and thusprovides a weather proof cover fo-r the tubular casing. Preferably agasket 54 is provided between the confronting surfaces of the attachingflange 46 and the rim 49 of said cover to prevent the entrance ofmoisture to the casing,

the cap screws 50, however, constituting a good electrical connectionbetween said cover 48 and the collar 40. The cap 48 is provided with acentral terminal clamping screw 56 which is adapted to be connectedelectrically by a lead 58 with the high tension line from which power isto be derived.

The base portion 10 of said casing is further provided with an annularinternal bracket 60 which is spaced below the upper end thereof andwhich forms the support for the ycapacitive unit of the transformer.Said unit includes a vertical cylindrical insulating tube 62 which issupported at its lower end by said bracket 60 andwhich extends upwardlyto a point just beneath the cap 48 of said cas`- ng and is concentricwith and has its sidewall spaced apart a substantial distance from saidouter casing. Said tube 62 is formed with a reduced lower end portion 64on which an annular supporting collar 66 is secured. Said collar 66 hasan outstanding` flange 68 that overlies the supporting bracket 60 of thecasing and is secured removably thereto by means of clamping screws 70.The outstand-A ing flange 68 is provided with a series of spacedperipheral passages 7 2 which provide for fluid communication betweenthe portions of the casing above and below said flange.

In accordance with the present invention the insulating tube 62 ispreferably built up of bakelized paper or some similar insulatingrmaterial which can be built up in layers. Spaced cylindrical condenserplates of metal foil or gauze are interposed between successive layersof insulating material to provide a plurality of serially connectedparallel condensers which are arranged along the length of the tube andare supported by and are in` sulated from each other and from thesurrounding casing by said tube. The disposition of the condenser plateswithin the insulation of the tube is more clearly illustrated in Fig. 8,which shows somewhat diagrammatically a lon gitudin al section through awallv of the tube 62 in which three sets of vertically spaced concentricinner and outer cylinders a, b, c, are 1provided between which threeintermediate vertically aligned cyliir ders el, e, f, are arranged whichoverlie the proximate ends of the adjacenI sets of said inner andvoute'rcylinders. As thus arranged each intermediate cylinder in conjunctionwith each set of inner and outer cylinders constitutes two .condensersin parallel which are designated at C1, C2, C3, C4 and C5. Theintermediate plates (Z and c which are common to two sets alsoconstitute means for connecting the parallel condensers in series.`

The inner and outer cylinders a of the upper set areelectricallyconnected together at their upper ends by means of a metal plate havingthe downturned side wall 7 4 which isembedded-in the material of thetube- 62 and overlies the outermost condenser cylinder a, and thehorizontal bottom wall .7 6 which overlies the upper end of theinsulating tube 62 and is in electrical contact with the innermostcylinder a. Said bottom wall 76 is provided with a large central passage78, whereby to leave the insulating tube open at the top. The bottomwall 76 of said tube also carries a plurality of radially outstandingresilient strips 8O having the horizontal end portions 82 which overlieand are in pre. sure engagement with the inwardly directed flange 44 ofthe upper collar 40, thus establishing electrical connection between thetwo upper condenser cylinders a and the casing terminal 56 through saidcollar 40 and cap 48. The'base portion 10 of said outer casing isprovided near the lower end thereof with a'raised bottom 84 having aperipheral downwardly refleXed flange 86 which is secured in av fiuidtight manner to the inner side of said base portion, as by welding. Saidbottom 84- also constitutes the support for an inductive potentialtransformer. Said transformer includes a laminated core frame 88 whichsuitably fiXed to said bottom wall 84 on a base 90. The upper leg ofsaid core frame carries a secondary winding 92 having the low tensionleads 94, and a primary winding 96 whichvis disposed about and isinsulated from said secondary winding having one of its leads 98connected electrically with the lowermost intermediate condensercylinder f, and its other lea-d 100 connected wfth a ground terminal 102of the base portion 10. As thus connected the primary winding 96 of saidtransformer is connect-ed in series with the condensers of the tube 62to ground. The lowV tension leads 94 are molded in an insulating bushing104 which is suitably connected in a fluid tight manner with the sidewall of said casing.

Preferably the cuter enclosing casing is completely lills the casing.

filled with an insulating fluid, as an insulating oil or gas, to a pointabove the top of the insulating tube 62. As herein shown a body of oil106 is provided Which substantially The oil is, therefore, free tocirculate by thermal action due to the heat-ing of the tube 62 resultingfrom the dielectric losses in the insulating material thereof. By theprovision of the open passage 78 at the top of the tube and theperipheral passages 7 2 in the supporting iiange G8 at the bottomthereof, the heated oil in the interior of said tube is free to rise,being replaced by oil from outside said tube which is cooler by reasonof its contact with the outer casing of the transformer.

The combined use of inductive and capacitive transformer units, as abovedescribed, has definite advantages. If the potential transformer is tobe used, for example, on a 110,000 volt line With a normal potential toground of approximately 63,500 volts, by designing the inductivetransformer with a ratio of 13,500 to 110 volts, a lovv voltage poiverof approximately 100 volts amperes can be obtained with a primarycurrent of only .03 amperes which, With the arrangement of condensersshown, is commercially feasible.

The transformer above described provides a very simple and inexpensivearrangement for deriving lovv voltage power from a high voltage line andone Which presents no difficult problems of insulation and isconsequently relatively inexpensive. By enclosing the inductive and,capacitive transformer units in a single casing it is possible toentirely eliminat-e expensive terminal bushings and to provide a verycompact and troublefree apparatus.

Certain features of the present invention are described in myconcurrently filed application Serial No. 499,143.

The construction and arrangement of the capacitive transformer may bewidely varied Without departing from the scope of the invention.

I claim:

1. In a voltage transformer, the combination of an upstanding enclosingcasing having a terminal at its upper end for connection to a .highpotential line, an insulating shell vertically extended in said casinghaving plates of conducting material Within the insulating materialthereof comprising .seri-V ally connected condensers, means electricallyconnecting the uppermost plate with. said casingT terminal, meanselectrically connecting the loivermost plate of said shell to groundincluding the primary Winding of an inductive transformer, and asecondary Winding for said transformer having loiv tension terminalsthat are extended externally of said casing.

2. In a'voltage transformer` the combinaing.

tion of an outer tubular casing having` an insulated high tensionterminal at its upper end, an insulating shell extended vertically insaid casing having concentric overlapping metal plates embedded in andinsulated from each other by the insulation of said tube, meanselectrically connecting the uppermost plate with said high tensionterminal, .and means electrically connecting the lowermost plate toground'including the primary Winding of an inductive potentialtransformer, said transformer also having a lovv tension secondaryWinding, a terminal of which is extended exteriorly of said casing.

3. In a voltage transformer, the combination of an enclosing casingcomprising a lower metallic base portion and an upper insulating portionhavinga high tension terminal at the top thereof, a tube of insulatingmaterial vertically extended in said casing and spaced apart from theside Walls thereof, said tube having a series of concentric spaced andoverlapping metallic plates embedded in the insulating material thereofwhich comprise serially connected condensers disposed along the lengthof said tube, an inductive transformer located in the base portion ofsaid casing including a primary Winding Which is connected in serieswith said condenser plates to ground, anda secondary Winding havinga lowtension terminal thereof extended exteriorly of said cast. In a voltagetransformer, the combination of an outer tubular casing having a baseportion and an upper insulating portion, a cover for the upper open endof said casing having a high tension terminal, a capacitive transformerlocated in the upper insulating portion of said casing and extendeddown- Wardly into said base portion, said transformer comprising` atubular insulating shell having concentric overlapping metal insertswhich are embedded in and are spaced apart by the insulating material ofsaid tube, and a step-down potential transformer of relatively lovvvoltage located in the base portion of said casing having its primaryWinding connected in series With said capacitive transformer and havinga lovv tenson secondary a terminal of which is extended exteriorly ofsaid casing.

`5. In a voltage transformer, the combination of an upstandinfy tubularcasing comprising a lower metallic base portion and an upper insulatingportion, a capacitive transformer located in the upper portion of saidcasing comprising a tubular insulating shell having spaced concentricand overlapping metal inserts embedded in and insulated by the material.thereof, an inductive transformer of relatively lovv potential locatedin the base portion of said casing having a primary vvinding which iselectrically connected in series with said capacitive transformer andhaving'a low tension secondary Winding, a terminal of which is extendedeX- teriorly of said casing.

6. In a voltage transformer, the combination of an upstanding tubularenclosing casing having a lower metal base portion and an upperinsulating portion, a cap forming a closure for the upper end of saidcasing having a high tension terminal, a base plate forming a fluidtight closure for the bottom end of said casing, an inductivetransformer located in said base portion on said base plate havingprimary and secondary windings, a capacitive transformer located in saidcasing above said inductive transformer comprising a cylindrical tube ofinsulating material which is concentric with and is spaced apart fromthe side wall of said casing, said tubey having concentric cylindricalmetal inserts arranged in staggered and overlapping relation along saidtube and insulated from each other by the material of said tube, meansconnecting the uppermost cylinder of said tube electrically with saidcasing terminal and Ineanselectrically connecting the lowermost cylinderof said tube in series with the primary winding of said transformer7said transformer having secondary low tension terminals one of which isextended to the outside of said casing.

7. In a voltage transformer, the combination of an outer tubularenclosing casing comprising a lower base portion, an upper 1nsulatingportion and an intermediate connecting portion, closures for the upperand lower ends of said casing, a high tension terminal at the upper endof said casing, a capacitive transformer located in said insulating andconnecting portions comprising a vertically extended insulating tubehaving serially connected condenser plates embedded in and insulatedfrom each other by the material of said tube, means electricallyconnecting the uppermost plate of said condensers with said casingterminal, means connecting the lowermost condenser plate to groundincluding the primary winding of a step-down transformer, saidstep-downtransformer having a secondary winding and having terminalswhich constitute the low tension terminals of said voltage transformer,and a fluid insulating m-edium occupying said casing and in which saidcapacitive and step-down transformers are immersed.

8. In a voltage transformer, the combination of an upstanding tubularenclosing casing comprising a lower base portion, an upper insulatingportion and an intermediate connecting portion, said base portion andintermediate portion having a breakable connection therebetween, aninductive transformer located in said base portion having primary andsecondary windings, a capacitive transformer located mainly above saidbase portion comprising an insulating vertically extended tube which isspaced apart from said casing and is conterminous with the Lipper endthereof having a series of concentric and overlapping condenser platesvertically spaced along the length thereof and insulated from each otherby the material of said tube, means supporting said tube removably insaid casing, a metal collar carried by the upper end of said insulatingportion, a cap secured to said collar constituting a closure for theupper end of said casing having a high tension terminal carried thereby,a metal plate carried by the upper end of said tube which iselectrically connected with the uppermost condenser plate thereof, meansarranged to connect said plate with said casing terminal includingresilient abutment contact members and means electrically connecting thelowermost condenser plate of said tube through the primary of saidinductive transformer to ground.

"9. A voltage transformer comprising the combination of an inductivetransformer of relatively low voltage having primary and secondarywindings, a capacitive transformer including an insulating supportingmember which upstands above said inductive transformer and which hasoverlapping metallic inserts comprising condenser plates carried by thematerial thereof, a high tension terminal electrically connected withthe uppermost plate of said transformer, and means connecting thelowermost plate of said condenser electrically with the primary windingof said inductive transformer, the terminals of said secondary windingconstituting the low tension terminals of the voltage transformer.

10. A voltage transformer comprising as a unitary apparatus thecombination of an inductive transformer having primary and secondarywindings which are insulated for relatively low voltages, a capacitivetransformer including an insulating support upstanding above saidinductive transformer having a high tension terminal at the top and alow tension terminal at the bottom which is connected to said primarywinding, the terminals of said secondary winding constituting the lowtension terminals of the Voltage transformer.

11. A voltage transformer comprising as a unitary apparatus thecombination of an inductive vtransformer having primary and secondarywindings which are insulated for relatively low voltages, a capacitivetransformer comprising an insulating shell vertically extended abovesaid inductive transformer and having plates of conducting materialcarried thereby comprising serially connected condensers, means forelectrically connecting the uppermost condenser plate with a hightension line, and means electrically connecting the lowerinost plate toground including the primary Winding of said inductive transformer, theterminals of the seconary winding of said transformer constituting thelow tension terminals of the voltage transformer.

12. In a voltage transformer, the combination of an enclosing casing, aninsulated high tension line terminal at the top of said casing, aninductive transformer located in the hase of said casing having primaryand secondary windings, and a capacitive transformer located in saidcasing intermediate said high tension terminal and said inductivetransformer, and connected electrically in series with said primarywinding, the terminals of the secondary winding of said inductivetransformer constituting the low tension terminals of the voltagetransformer.

13. In a voltage transformer, the combination of an enclosing casinghaving an insulating side wall, a high tension terminal located at theupper end of said casing, an inductive transformer located in the baseportion of said casing having primary and secondary windings, and acapacitive transformer located in said casing intermediate said terminaland inductive transformer and having its upper terminalelectricallyconnect ed with said high tension terminal and its lowerterminal electrically connected inseries with the primary winding of theinductive transformer, the terminals of said transformer secondaryconstituting the lower tension terminals of the voltage transformer.

14. In a voltage transformer, the combination of an enclosing casingadapted to contain oil, an insulated high tension line terminal at thetop of said casing, an inductive transformer contained in the lowerportion of said casing having primary and secondary windings which areinsulated for relatively low voltages, and a capacitive transformerlocated in said casing intermediate said terminal and inductivetransformer having one terminal thereof electrically connected to -saidline terminal and another terminal electrically connected with theprimary winding of said inductive transformer, the terminals of saidsecondary winding constituting the low tension terminals of the voltagetra-nsformer.

15. In a voltage transformer, the combination of an upright enclosingcasing adapted to contain an insulating fluid, an insulated high tensionline terminal carried by said casing at its upper end, an inductivetransformer located in the lower portion of said casing having primaryand secondary windings which are insulated for relatively low voltages,a capacitive transformer located in said casing intermediate saidinductive transformer and said high tension terminal having an upperterminal electrically connected with said high tension terminal and alower terminal which is connected to one end of said primary winding,the secondary ter- GUSTAV E. JANSSON.

